THE JOINTS 159
the navicular to the second metatarsal bone, and an internal ligament binds it to the internal cuneiform.
Plantar Metatarsal Ligaments.—The long plantar ligament ends in fibres which also connect the sheath of the tendon of the peroneus longus to the bases of the third and fourth metatarsal bones. A band of fibres derived from the long plantar ligament runs to join the external plantar metatarsal ligament, which is an apo-neurotic band on the fourth metatarsal bone. Another band from the long plantar ligament lies along the third metatarsal bone and forms the internal plantar metatarsal ligament.
Humphry (340) draws attention to the following points regarding the mechanics of the foot in the Chimpanzee:—
(1) The shape of the talus throws the weight on the outer border of the foot.
(*2) The talus and calcaneus are more for support than progression.
(3) The calcaneus rolls outward on its lower surface.
(4) The calcaneus is reduced, like its hoinotype the pisiform, to a lever for muscles.
(5) The talus, navicular and calcaneo-navicular ligament transmit weight.
(6) The posterior surface of the talus slopes downwards and inwards.
(7) The action of the calf muscles on the foot is unfavourable for lifting weight or propelling the body.
(8) There is no plantar arch,
(9) The bones, joints and muscles of the hallux act like those of the pollex.